Astronomy and Astrophysics – Astrophysics
Scientific paper
Feb 1999
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999eso..pres....5.&link_type=abstract
ESO Press Release, 02/1999
Astronomy and Astrophysics
Astrophysics
Scientific paper
Scientists Meet in Antofagasta to Discuss Front-Line Astrophysics
To mark the beginning of the VLT era, the European Southern Observatory is organizing a VLT Opening Symposium which will take place in Antofagasta (Chile) on 1-4 March 1999, just before the start of regular observations with the ESO Very Large Telescope on April 1, 1999.
The Symposium occupies four full days and is held on the campus of the Universidad Catolica del Norte. It consists of plenary sessions on "Science in the VLT Era and Beyond" and three parallel Workshops on "Clusters of Galaxies at High Redshift" , "Star-way to the Universe" and "From Extrasolar Planets to Brown Dwarfs" .
There will be many presentations of recent work at the major astronomical facilities in the world. The meeting provides a very useful forum to discuss the latest developments and, in this sense, contributes to the planning of future research with the VLT and other large telescopes.
The symposium will be opened with a talk by the ESO Director General, Prof. Riccardo Giacconi , on "Paranal - an observatory for the 21st century". It will be followed by reports about the first scientific results from the main astronomical instruments on VLT UT1, FORS1 and ISAAC.
The Symposium participants will see the VLT in operation during special visits to the Paranal Observatory. Press conferences are being arranged each afternoon to inform about the highlights of the conference.
After the Symposium, there will be an Official Inauguration Ceremony at Paranal on 5 March Contributions from ESO
ESO scientists will make several presentations at the Symposium. They include general reviews of various research fields as well as important new data and results from the VLT that show the great potential of this new astronomical facility.
Some of the recent work is described in this Press Release, together with images and spectra of a large variety of objects. Note that all of these data will soon become publicly available via the VLT Archive.
The text below summarizes the individual projects. Comprehensive texts with all photos and diagrammes are available in nine separate web documents ( ESO PR Photos 08/99 to 16/99 ) that may be accessed via the links at the top of each section. The degree of detail and level of complexity of the texts depend on the subject and the available materials. 1. Dwarf Galaxies in the Local Group
ESO PR Photo 10a/99
ESO PR Photo 10a/99 The Antlia Galaxy (FORS1 colour composite) . Access full text and PR Photos 10a-d/99
In addition to large spiral galaxies like the Milky Way Galaxy, the Andromeda Galaxy and Messier 33, the Local Group of Galaxies contains many dwarf galaxies. The VLT has observed two of these, Antlia and NGC 6822 .
Antlia is a low-surface brightness, spheroidal dwarf galaxy that was only discovered in 1997. While it contains a large amount of atomic hydrogen at its centre, no young stars are found, and it appears that most of its stars are old. This is unlike other dwarf galaxies in the Milky Way neighbourhood, as star formation is expected to occur within dense hydrogen clouds. Further observations will be necessary to understand this unusual characteristics.
The VLT also obtained images of an irregular dwarf galaxy in the Local Group, NGC 6822, as well as spectra of some of its stars. This galaxy is of the "irregular" type and is situated at a distance of about 2 million light-years.
A comparison of the spectra of supergiant stars in NGC 6822 shows that many spectral lines are much weaker than in stars of similar type in the Milky Way, but of similar strength as in stars in the Small Magellanic Cloud. This confirms an earlier finding that NGC 6822 has chemical composition (a lower "metallicity") that is different from what is observed in our Galaxy. 2. The Double Stellar Cluster NGC 1850 in the LMC
ESO PR Photo 15/99
ESO PR Photo 15/99 NGC 1850 (FORS1 colour composite) . Access full text and PR Photo 15/99
NGC 1850 is a double cluster in the Large Magellanic Cloud, a satellite galaxy to the Milky Way Galaxy. This cluster is representative of a class of objects, young, globular-like stellar associations , that has no counterpart in our own Galaxy.
The VLT images show faint nebulosity in this area, with filaments and various sharp "shocks". This offers support to the theory of supernova-induced star birth in the younger of the two clusters. It is estimated that about 1000 stars in the older of the clusters have exploded during the past 20 million years. 3. The Barred Galaxy NGC 1365
ESO PR Photo 08a/99
ESO PR Photo 08a/99 The Barred Galaxy NGC 1365 (FORS1 colour composite) . Access full text and PR Photos 08a-e/99
NGC 1365 is one of the most prominent "barred" galaxies in the sky. It is a supergiant galaxy and is a member of the Fornax Cluster of Galaxies, at a distance of about 60 million light-years.
This galaxy has an intricate structure with a massive straight bar and two pronounced spiral arms. There are many dust lanes and emission nebulae in these and also a bright nuclear region at the center that may hide a black hole.
Several images of NGC 1365 have recently been obtained with all three astronomical instruments, now installed at the VLT UT1. They show the overall structure of this magnificent galaxy, and also the fine details of the innermost region, close to the centre. An infrared ISAAC image penetrates deep into the obscuring dust clouds in this area. 4. The colours of NGC 1232
ESO PR Photo 13a/99
ESO PR Photo 13a/99 Differential (UV-B) image of NGC 1232 (FORS1) . Access full text and PR Photos 13a-b/99
NGC 1232 is a large spiral galaxy in the constellation Eridanus (The River). With a diameter of nearly 200,000 light-years, it is about twice the size of the Milky Way galaxy. The distance is about 100 million light-years, but the excellent optical quality of the VLT and FORS allows us to see an incredible wealth of details.
Computer processed "colour-index images" have been prepared that show the "difference" between images of the galaxy, as seen in different wavebands. Since different types of objects have different brightness in different colours, this method is very useful to locate objects of a particular type and to obtain an overview of their distribution in the galaxy.
The distribution of star-forming regions and dust lanes in NGC 1232 are shown on two such photos. 5. A Selection of ISAAC Spectra
ESO PR Photo 11a/99
ESO PR Photo 11a/99 He I 1038 nm line in SN1987A (ISAAC spectrum) . Access full text and PR Photos 11a-c/99
Various observations were made with the ISAAC multi-mode instrument at the Nasmyth focus of VLT UT1 during the recent commissioning periods for this infrared multi-mode instrument. They impressively demonstrate the unique capabilities of this facility.
The new data include several infrared spectra of faint objects with interesting features.
A spectrum was obtained in the near-infrared region of the ring nebula around SN 1987A in the Large Magellanic Cloud. It consists of material blown off the progenitor star during its evolution. Of particular interest is a jet like structure in the dispersion direction which reveals the presence of a broad, blueshifted, HeI component which presumably originates in the shock ionized ejecta.
Another spectrum shows emission features in two galaxies at redshift z = 0.6 [1] that allow the determination of a rotation curve at this large distance. The 1 - 2.5 µm infrared spectrum of the radio galaxy MRC0406 at z =2.42 is also included. 6. The Cluster of Galaxies MS1008.1-1224
ESO PR Photo 09b/99
ESO PR Photo 09b/99 Centre of the Cluster of Galaxies MS1008.1-122 (FORS1 colour composite) . Access full text and PR Photos 09a-b/99
The study of "Deep Fields" is becoming a common tool in astronomy. Among the various sky fields that have been selected for detailed investigation of the faint and distant objects therein, is the FORS Deep Field that will be observed during FORS1 "guaranteed time", available to astronomers from institutes that built this instrument.
In preparation of this work, an imaging programme was carried ou
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